Primes are for the very serious few who demand narrow DOF - and that is the FF DSLR photographer.
Primes offer more than just narrow DoF. They can be smaller and lighter than zooms covering their FL. They can have faster apertures than zooms covering their FL. Often, they are smaller/lighter
and faster.
Consider the M22/2...22mm f/2 on APS-C doesn't exactly deliver shallow DoF at 'typical' subject distances, but it's much smaller than any M zoom, and lets in 4 times as much light as the M18-55/M15-45 at 22mm...and 8 times as much light as the M11-22 at 22mm.
Also, where can I find a TS-E zoom? A 5x macro zoom? How about even a 1x macro zoom?
Sorry, but to believe that primes are only about narrow DoF is quite narrow minded.